Solvent extraction



Dec. 27, 1 949 H, R, DAv|s 2,492,787

soLvENT EXTRAGTION Filed Sept. 14, 1946 @zg a d4 55,' 3 37 55 ATTORNEY Patented Dec. 27, 1949 UNITED STATES SOLVENT EXTRACTIQNQY Hyman n. Davis, Jackson HeightsgW-N; Yrassignor# to ,The Lummus Company, lNew York;iNeY.,"a

corporation of Delaware Thisiinvention relates to-solvent extraction of hydrocarbon oils vand moreparticularly to the exe traction oflubricating oils.

the production of` lubricating loils vby customary solvent-extraction'processes; Mvarying 5 denandsi'for'oils of different character require frequent reconditioning of Ythe 'extraction' 'system toobtaini a required: end product. Asystem 1 Whiolrhasbeen conditione'dto handle one charge oil forthe production-`ofga lubricating oilV of givenm viscosity index must tbe-reconditioned in order to handle;anothercharge'oil and produce a 1ubri' eating' 'oil' of4 different viscosityj'indexi In add` tioirto that ldisadvantage;*expensive tankage is required to retain one charge oil inireservel whilet15' anotheris being processed.

As an alternative 'toi thisfsystem; a method may be used` whereby two or.r more extraction stages.: are-treated'-as-onesystem.'4 The extract solution from-each stage-"isfimmediately combinedv and .20 passed'to a single'-, or 4doubleeeffect krecovery i system: Thisfmethod 4'has the disadvantage; of recycling to each lextraction stage an extract that' f' isnotgofa proper composition for each stagealone sinceitv'is a blend ofgtheioriginaliextractsfrom 25 each 'ofthe aforesaid extract'stages.

An 'important` object ofY my invention is toprovide in a simple, satisfactory vand economical" manner for the solvent' extraction of different lubricating -oils simultaneously Vfrom different' .30 charge voils Within a single system.

A 'furtherobject of'my invention is tov provide@ irr^such simultaneous processing ofA "diierent chargeoilsffor recycle of the extracts of the dif#v ferent-chargeV oils .toi the appropriate extraction 35 zones."

A still" furtherobject of'my invention is to provide for-such simultane ousprocessing of` differentV charge' oilslwhile, at the same time'maintaining j all the benefits of a multiple effect evaporator re.L 40 covery system-"and-ina manner-to -require Aa minimum of equipment.

Otl'lerrobjectsiand advantages of my invention willi-appear lfrom-the following description `taken with the accompanying `drawingv showing a Vflowl5Y sheet of a suitable system for carrying Vout'my inventionv.= y

According to the invention, a heavy charge'oil anch '1a light-'charge :oil are introduced simulf' taneously' into -separate extractionwzones and,50 within each zone,` contact of the'charge-with the 'solvent-*isfreffectedfunder ythermaly conditions suited-tof ther-'particular' -'chargez The -Fra'filrlate7` phase'fis passed-fromeachzone, heated' and intro--A ducedtoia steam stripping/'zonalindividualetofthes 2-i extractionzone,ifor'separation of' 'solvent from theraifiate.or desired end product. The.ex. tract phase .is withdrawn from the heavy oil rextraction zone,.heated andintroduced to a higlifl pressure .vaporization zone, Whereinthe solvent is. vaporiz'e'd from .the extract, the latter being.; recycled 'to said .extraction zone ,Y inlwhi'ch it i originated. At thesame time, ,the extract phase is withdrawn :from .tlie' light foil 'extraction zone,Y

-passed in indirect heat exchangerelation to the vapor from..the.said. highrpressure vaporization zoneand then introduced to a low pressure vaporization zone wherein the solvent is '.vaporized I. fromthe extract. Fromthelow pressure vaporvization zone theextractis'recycled to. the light oil extraction zonewhre it originated. The .sol' vent recovered fromihe' extract Withinboth'the high pressure vaporzation zone and the low pres.- surevaporization zone is 'recycled to theextracf. tion. zones and heat-conditioned Iin the course of its"recycle` to regulateith temperatures Within.. the extraction zones;

In' th' oper-.ationlofihe system shown inthe drawing `the charge4 of heavy oil Ais continuously., introducedzthrough'line I to an extraction .column 2. Simultaneously; the light oil charge is'intro duced through `-line 3 'tof an extraction column 4.

Withinreach '.column counter-current contact is.l effected betvveenth'e respective charge andV the solvent. '.1 From ,theupper portion of column 2 the.; raffinate; phase, `comprising the lubricating loill component 'of the Ycharge and some solvent, is

forced by the pump through line 6 and a heater.. 1 to a stripping column. Steam is'introduced to the lowerportion of this stripping column through'theline Sfandthesteam and recovered` 1 solvent are passedv 01T fromthe top ,of the column through th .line I0`to a solvent recovery system, not shown. From the .bottom of the stripping column. the recovered l'rafr'iate .is' withdrawn through theline Il;

The extractfphase or "solution" within then'. co1umn2 iswithdrawnirom the bottom of the column and passed by the pumpzl2 through linel I3 'and 'a heater., Mito" a high'pressure chamber` l'having 4Vrectifyin'g `plates .I6` within the upperv portionlthereoi Solventvaporized bythe heat" suppliedybyv tlr'e' heater isi'passed 01T `from the" space abovethe' rectifying plates through-the overhead *line* 1 l. 'l Recovered4 extract is recycled by th'epumpfl through lines 'I9 and' 20. to the lower portion "ofe'xtraction 4colurnn 2 forfurther recovery'ofirainater From-'the' upper; portion .'of extraction Acolumn 4 the' raiiiiate phasecomprising the' lubricating oil component of the charge, together with some solvent, is passed by the pump 2l through line 22 and heater 23 to the upper portion of a stripping column 2li. Steam is supplied to the lower portion of the column through line 25, and the steam and recovered solvent are passed off from the top of the column through line 26 to the solvent recovery system. From the bottom of the stripping column the recovered raiinate is withdrawn through line 21.

The extract phase within the column 4 is withdrawn fromthe bottom of the column and passed by the pump 28 through line 29, a condenser 30 and an evaporator 3| to a low pressure chamber 32 having rectifying plates 33Y withinV the upper portion thereof. As shown, this chamber, together with the high pressure chamber i5, may be dened by a single column, partitioned as at 34. The evaporator 3| is of a shell-and-tube type and the line 29 delivers `to the tube side while the line l 'l which conducts the hot solvent vapors from the high pressure chamber l delivers to the shell side of theevaporator. Thereby, the extract phase delivered by the line 29 is heated to vaporize the solvent component thereof by passing it in indirect heat exchange relation with the hot vapor from chamber l5. Thus, the heat input obtained from the singlev heater i4 is utilized to vaporize the solvent component from the extract phase delivered from both of the extraction columns.

Within the low pressure lchamber 32 the extract is recovered from the solvent and settles within the lower portion of the chamber. A pump 35 recycles the recovered extract through lines 36 and 3l' to the lower portion of the extraction column 4, where it originated, for increasing the yield of rai-linate.

The solvent recovered from the extract solution within the highV pressure chamber i5, after passing through the evaporator 3l, is conducted through line 38, provided with a valve, to a solvent accumulator 3S. The solvent vapor recovered within the low pressure chamber 32 is passed from the space above the rectifying plates 33 through the line 40 to the condenser 30. There it imparts heat to the extract delivered through the line 29 and is liquefied and then passed through the line 4l to the accumulator 39. A pump 42 passes the solvent from the accumulator through a line 43 which is connected by branch lines 44 and 45 to the extraction columns 2 and 4 respectively. Thereby, the recovered solvent is recycled to said columns. Within each of said branch lines there is a heat exchanger 46 through which either heating or cooling fluid may be passed in indirect heat exchange relation to the solvent. By control of the ltemperature of the delivered solvent, proper thermal conditioning of the extraction columns is obtained.

Elimination of the extract from the system is effected through a stripping column 4l. A line 48 is connected to the extract recycle line I9 and leads to the upper portion of said stripping column. A line 49 also connects the extract recycle line 3S with said line 48. By meansof a valve 50 in the line 43 and located adjacent the point of connection of said line with the line I9, and by means of a valve 5l in the line 43, the

delivery of the extract from the system to the solvent recovery system. Through line 54 the extract is withdrawn from the column 41 and from the extraction system.

It is thus apparent from the foregoing disclosure of my invention that I have discovered a new method providing for the solvent extraction of two diierent oil stock charges in one system while separately treating the extract solutions from each stage and, at the same time, maintaining al1 the advantages of a double effect recovery system for the extract solutions.

As an example of the employment of the system for the processing of two particular charge Y oils, it will be assumed that the heavy charge oil is a deasphalted petroleum residuum, that the light charge oil is an S. A. E. l0 petroleum distillate and that iurfural is employed as the solvent. Then, assuming that the heavy oil is charged to the extraction column 2 at the rate of 1,000 bbls. per clay, that the light oil is charged to the extraction column 4 at the rate of 2,000 bbls. per day, and that the solvent is charged to each of said extraction columns at the rate of 4,000 bbls. per day, the following approximate thermal and pressure conditions are maintained for optimum performance of the system. A temperature of.

F. is maintained within the lower portion of the extraction column 2 and a temperature of 285 F. is maintained within-the upper portion of said column. The heat input of the heater should be such that the rainate solution is introduced into the stripper 8 at 430 F., and the heat input of the heater I4 should be such that the.

extract solution is introduced into the high pressure chamber i5 at 450 F. A pressure ranging from 30 to 50 lbs. gage, is preferably maintained within this chamber. For the light oil extraction column 4 suitable temperatures are 150 F. for the lower portion of the column and 220 F. for the upper portion of the column. The heat input of the heater 23 is also preferably such that the rainate solution is introduced into the stripper 24 at 430 F., While the heat input by the heat exchanger 3| is preferably such that the extract solution is introduced into the low pressure flash chamber 32 at 340 F'. Preferably this chamber is maintained at atmospheric pressure, or only a few pounds above atmospheric.

While furfural is mentioned as a satisfactory solvent for employment in the process, other wellknown solvents such as nitrobenzene, phenol, crotonaldehyde, chlorex, cresylic acid, liquid sulfur dioxide and benzene, for examples, as well as numerous other solvents, may be employed satisfactorily. It will also be understood that the employment of the process is not limited to the extraction of lubricating oils. The process may be employed to advantage in processing a variety of different charges to obtain end products other than lubricating oils.

It is, of course, to be understood that the present disclosure of my invention is merely illustrative and in no wise limiting and that the invention comprehends such modifications as will come within the scope of the following claim:

I claim:

In the recovery of solvent and products from the solvent extraction of two independent hydrocarbon oils, in which a relatively heavy charge oil is contacted with a solvent within a first extraction zone at relatively high temperature and simultaneously a lighter charge oil is contacted l with solvent within a second extraction zone at lower temperature thereby forming an extract so- .l lution and a ranate solution in each zone, the

amava? process which comprises passing the extract. solution from the rst-mentioned extraction zone through a heating zone and thence to a vaporization zone and there vaporizing the solventjrom the extract under relatively high pressure, simultaneously passing the extract solution from the second-mentioned extraction zone through a plurality of heating zones and thence to another vaporization zone, maintaining the secondi-mentioned vaporization zone under lower pressure than the first-mentioned vaporization zone, and supplying the heat for the extract solution for vaporization of the solvent therefrom within said lower pressure zone by passing the extract solution in indirect heat exchange relation Vvwith the vaporized solvent from the rst and second vaporization zones, and recycling a portion of the extracts from said vaporization zones to the respective extraction zones.

HYMAN R. DAVIS.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS 

